I have the yarn on order for a Ravenclaw Harry Potter. The reason that it's "double thick" is that it is done on a circular needle, then laid flat and stitched shut at the ends. So you would need to cultivate the skill to use a circular needle, change colors and do the three needle bind off in order to do the Prisoner of Azkaban scarf. All of this is possible if you feel up to it, and you can find the videos on this site to help you.
When does this scarf need to be finished? For the book launch?
On the needles: Tempting for Kate, cabled jacket for Emma